(NOUN) A stubby thumblike protrusion, usually originating from the male groin, which acts as a substitute for a penis.
(VERB) To thub; to thrust with a thub, generally part of a sexual act but doesn't have to be.

Thighs that rub together due to an excessive amount or fat deposited at the inner top portion of the thigh. You may observe thubs best in the summer by walking behind women 200 lbs or more. Thubs may also be seen in men.

Thighs-that-rub!

"Her thubs are feeding her hungry bum!" or "I don't see how any guy could have sex with that lady, how would they get past her thubs?"